1. Field of the Invention
The present invention is concerned with vehicles designed for alternate travel on a roadway or railroad rails (e.g., railcar movers used in industrial settings for short movements of railcars), and improved rail wheel assemblies which may be used with such vehicles. These vehicles are equipped with wheel assemblies for engaging a roadway during roadway travel, and for engaging railroad rails during railroad travel, as well as rail wheel assemblies which may be selectively lowered to engage and ride upon the railroad rails. More particularly, the invention is concerned with such vehicles and rail cars, as well as improved rail wheel assemblies finding particular utility in these vehicles. Broadly speaking, the improved rail wheel assemblies of the invention are negative cambered or inwardly inclined such that the rotational axes thereof are at small (less than 6xc2x0) oblique angles relative to the horizontal so that the upper ends of the rail wheels are slightly inboard of the lower ends thereof adjacent the rail.
2. Description of the Prior Art
A number of dual use vehicles have been proposed in the past and which are capable of traveling on regular roadways or alternately upon railroad rails. Generally speaking, these vehicles include more or less regular roadway wheels which also will travel on rails, as well as selectively usable rail wheels which may be lowered onto rails as needed.
One class of dual use vehicle of this type is railcar movers. These are used in the context of industrial plants or grain elevators for example, in order to move one or more railcars short distances within the associated rail yards. Railcar movers are considerably less expensive than standard locomotives, but nevertheless capable of moving rail cars the short distances required. Existing railcar movers are equipped with various sizes of rail wheels (e.g., 22 inch) having a slightly different flange configuration than the rail wheels used with railcars.
A problem with conventional railcar movers is known as xe2x80x9cwheel climbxe2x80x9d, which refers to the tendency of the rail wheels to ride up on the rails when a curve and/or side load is encountered. This problem can be so severe that the railcar movers cannot negotiate some tight curves, or the load on the mover must be reduced to avoid derailment.
The following references depict various rail wheel assemblies which employ inclined rail wheels: U.S. Pat. Nos. 3,945,326, 4,058,065, 1,952,043, 2,72,780 and 2,842,393; and French Patent No. 685,306 and German Patent No. 821,163.
The present invention overcomes the problems outlined above and provides a vehicle designed for alternate travel on a roadway or railroad rails, the vehicle including a frame, and a dual use set of wheel assemblies oriented for engaging the roadway during roadway travel, and for alternately engaging the rails during railroad travel. The vehicle also has a set of rail wheel assemblies, and a rail wheel shifting mechanism operable to move the rail wheels into a tracking position in engagement with the rails for the railroad travel, and to move the rail wheels to a retracted position for roadway travel. The improved rail wheel assemblies of the invention include a mounting assembly for at least certain of rail wheels serving to orient the rotational axes of the associated rail wheels at small oblique angle relative to the horizontal with the inner margins of the upper ends of the rail wheels being inboard of the lower ends thereof adjacent the rails. This has been found to significantly inhibit the rail wheel climb.
In more detail, the rail wheel set of the invention comprises two pairs of rail wheels, each of the rail wheels of each pair having a mounting assembly associated therewith. This mounting assembly preferably includes a fixed, obliquely oriented spindle which is supported upon a shaft; the shaft is in turn mounted for up and down pivotal movement, thereby permitting the rail wheels to move between the retracted, roadway travel position, and the lowered railroad travel position.
The roadway/railroad wheel set arc preferably in the form of two pairs of wheels mounted between the fore and aft rail wheel pairs. The wheels are conventional and include pneumatic tires. At least one set of these wheel pairs is powered so as to permit movement of the vehicle both on a roadway and on rails. Further, in order to provide roadway steering, the front and/or rear pair of wheels is steerable.